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Author Topic: B&W Pi-network ID  (Read 11814 times)
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KA8WTK
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« on: April 17, 2011, 01:06:29 PM »

  I have a B&W Pi-network with the large silver plated coil made from tubing. It measures 10" in overall length, 4 1/2" wide and 8" tall. So what's my problem......
  The copy of a B&W catalog I can find shows pictures of the various networks in the 850 series. The picture with the large tubing coil is marked as an 851. However, the dimensions for the 851 are 7 x 3 x 3 1/2". My coil has the same dimensions as the 852 network but does not match the picture in the catalog.
  Could this be an 852 assuming the catalog picture is wrong? Maybe it isn't even a B&W but I would not know what else it could be.

Bill
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Bill KA8WTK
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« Reply #1 on: April 17, 2011, 01:13:14 PM »

A picture is worth a thousand words.....

Carl
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KA2DZT
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« Reply #2 on: April 18, 2011, 04:38:42 AM »

Bill,

Your post is not very clear.  Is there a picture of the 852 that doesn't exactly look like your coil, or are you saying your coil doesn't look like the 851 and the 852 isn't pictured??

My guess, if your coil measures as a 852, it probably is a 852 or something very close.  Never rule out that you may have a coil that B+W made special for some company and it may differ from the standard catalog model.  Especially, if it doesn't have a B+W logo or model number.  Companies made products using standard parts, like transformers, chokes, and other large parts. But, they had the parts made to their specs with special part numbers, so it wouldn't look like they were just using off-the-shelf parts.

Fred
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W4AAB
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« Reply #3 on: April 18, 2011, 05:10:11 AM »

I am sending Bill a picture that I have of a B&W 852. Bill, it is in a different format, so you will need to open it with Windows and Fax Viewer. I have an 850A, which I have .jpg's of.
                                               Joe W4AAB
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WA1GFZ
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« Reply #4 on: April 18, 2011, 09:35:23 AM »

I have the specs on each network if you post a picture I can match them.
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KA8WTK
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« Reply #5 on: April 18, 2011, 12:23:35 PM »

Joe ..... sent you the address.

Fred, you may have hit it. There are no markings on the unit like you would normally see.

All, I will post pictures tonight.

Bill
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Bill KA8WTK
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« Reply #6 on: April 18, 2011, 06:29:24 PM »

The Pics.....


* 8643.jpg (96.23 KB, 800x600 - viewed 583 times.)

* 8644.jpg (78.46 KB, 800x600 - viewed 563 times.)

* 8645.jpg (55.55 KB, 600x800 - viewed 557 times.)
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Bill KA8WTK
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« Reply #7 on: April 18, 2011, 06:33:27 PM »

Another and the catalog page ....


* 8646.jpg (58.57 KB, 600x800 - viewed 551 times.)

* Image3.jpg (133.66 KB, 570x870 - viewed 676 times.)
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Bill KA8WTK
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« Reply #8 on: April 18, 2011, 06:48:03 PM »

It sure looks like an 851.

BTW, the only ID on those from B&W is a decal which usually disintergrates when someone washes the assembly prior to listing on fleabay.

Carl
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KA8WTK
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« Reply #9 on: April 18, 2011, 06:58:38 PM »

Yeah, it looks like the 851 picture in the catalog. Now look at the dimensions at the bottom of the page. This one is the same size as they list for an 852. Hence my confusion.
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Bill KA8WTK
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« Reply #10 on: April 18, 2011, 07:30:41 PM »

852
7uh, 3.72, 2.34, 1.34, .95uh
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KM1H
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« Reply #11 on: April 18, 2011, 08:26:10 PM »

851 if you look at the coils and # of turns, 80-15 is all tubing and 10 is wide strap, the QRP one looks completely different. Forget the dimensions, the turns look right.
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KA8WTK
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« Reply #12 on: April 18, 2011, 08:30:34 PM »

Humm .....
If I am measuring this correctly, I figure just about 7 uh for the coil using a 198 pf cap across it. The GDO has about a 4.2 mHz dip. (Figure some "slop" for the test leads.)

That would make it an 852 and the catalog pictures are reversed for 851 and 852. And the dimensions would make sense.
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Bill KA8WTK
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« Reply #13 on: April 18, 2011, 08:47:52 PM »

851 is a low power network 2500 to 5000 ohms. 250W AM
852 cap values, 268pf, 144, 73, 48.5, 36pf  (1500 to 3000 ohms plate load)
Just found another spec sheet.
Load cap at
3.9MHz=1300pf
7.15=710
14.2=360
21.21=230
28.5=178
So 300pf plate tune and 2000pf load should do it.
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KA2DZT
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« Reply #14 on: April 19, 2011, 05:08:26 AM »

  I have a B&W Pi-network with the large silver plated coil made from tubing. It measures 10" in overall length, 4 1/2" wide and 8" tall. So what's my problem......
  The copy of a B&W catalog I can find shows pictures of the various networks in the 850 series. The picture with the large tubing coil is marked as an 851. However, the dimensions for the 851 are 7 x 3 x 3 1/2". My coil has the same dimensions as the 852 network but does not match the picture in the catalog.
  Could this be an 852 assuming the catalog picture is wrong? Maybe it isn't even a B&W but I would not know what else it could be.

Bill


Bill,

I checked all my B+W catalogs,   (FYI)these coils where not made back in 1946.  I looked in other B+W catalogs.  Your catalog has the pictures mixed up.  My catalogs shows your coil as an 852 (I can clearly see the model number on the coil in the catalog pic), it's the only one with a ceramic back switch plate.   I studied your pictures against the pic in the catalog.  Your coil looks the same as the catalog pic except it's not exactly the same as near as I can see.  It seems that the tap locations may be a little different.  On your coil I'm not seeing a tap at the 4th turn from the front end.  This tap, (looking at the back end) is about at the 8 o'clock position and taps the 4th turn from the front end. this tap should be the 40 meter tap.  I also think I see the coil has 10 turns.  In your pics,  I think I'm only seeing 9 turns.

Check this stuff and let me know.
Hope some of this helps,

Fred
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WA1GFZ
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« Reply #15 on: April 19, 2011, 08:55:05 AM »

Note the early networks had big silver rotor contacts while newer ones have a stamped spring contact, Your mileage could vary.
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KM1H
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« Reply #16 on: April 19, 2011, 01:48:13 PM »

I see about 10 1/4 turns in the photo and the 40M tap is very visible in one of them.

No way is that a 250W coil.

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KA4RFA
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« Reply #17 on: April 19, 2011, 06:52:14 PM »

FOR SOME MORE INFO ON THE B+W 850 SERIES

GO TO K4HX's 4/16/11 post in the FOR SALE Section-

JIM-
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KA2DZT
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« Reply #18 on: April 20, 2011, 04:18:59 AM »

I see about 10 1/4 turns in the photo and the 40M tap is very visible in one of them.

No way is that a 250W coil.



Yes, I do see the 40M tap in the one pic,  not sure why I missed it.  The coil is rated at a KW.

Fred.
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